DE3229931A1 - SOLID OXYGEN SENSOR - Google Patents

Description

322993T

PATENT LAWYERS

1OOO BERLIN-DAHLEM 33 · PODBIELSKIALLEE 68 8O0O MUNICH 22 ■ Wl D E N MAYE RSTRASS E 49

European Atomic Energy Community (EURATOM)

BERLIN: DIPL.-ING. R. MULLER-BORNER

MUNICH: DIPI INS. HANS-HEINRICH WEY

DIPL.-INS. EKKEHARD KORNER

Berlin, August 9, 1982

Solid oxygen sensor

(Priority: Great Britain, No. 8124416, August 10, 1981)

9 pages of description with

19 claims

1 page summary

1 sheet of drawing

MP 27 844

BERLIN: TELEPHONE (O3O) 8312O88 CABLE: PROPINDUS TELEX: 184057

MUNICH: TELEPHONE (089) 225585 CABLE: PROPINDUS TELEX: 524-244

The present invention relates to electrochemical Solid-state devices for measuring oxygen activity, whereby these devices have a solid oxide electrolyte and oxides as the oxygen sensitive electrode material.

They are electrochemical cells for measuring the partial pressure of oxygen known, which are formed by a solid oxide electrolyte, the non-oxidizable electrodes has electronic conductors, for example from one of the Noble metals, especially Pt, exist.

The solid electrolyte is a ceramic oxide or a vitreous one Phase with pure ionic conduction, e.g. a solid solution of oxides that lacks oxygen ions.

These cells, hereinafter referred to as "oxygen sensors", have various disadvantages mainly due to the metallic Electrode material (Pt) are attributable to what their uses considerably restricts.

In fact, the measured oxygen partial pressures are inferior to the real values if traces of oxidizable substances such as Hp. CO, SO ₂ and hydrocarbons are present in the gas mixture to be analyzed.

When measuring the oxygen activity in CO / CO ^ -emisehen We will observe good precision in determining the ratio of the two gases, but the response times are for rapid changes in the gas mixture composition are very high.

If SO (χ = 2 or 3) in the gases to be analyzed is available, the response times are very long.

Many metals can poison the electrode material (Pt), and the use of the oxygen sensor in monitoring the reducing atmosphere in a metallurgical Application is sometimes very critical or impossible.

The electrode material (Pt) is particularly easily poisoned by Pb; because of this, the use of a such a device for monitoring exhaust emissions from a gasoline-powered machine, the gasoline contains organometallic Pb compounds, excluded.

In order to overcome these shortcomings and to produce a solid electrochemical oxygen sensor which, in conjunction with a wider range of uses can be used, according to the present invention, a new solid-state electrochemical device is proposed, in which the electrode material (generally a non-oxidizable electronic conductor such as a noble metal) Oxide materials with mixed ionic and electronic electrical conductivity is formed.

Such materials are either non-stoichiometric oxides (PrO ₉ »TbO ₉ or mixtures of these oxides, eg: TbO ₉ +

CeO ₂ _ _x ; ^Pr0 2_x ^{+ Ce0} 2-x ^ ^or 9 ^emiscnte oxides (LaCrO ₃ ; ^La 1-x ^Sr x ^Cr0 3 ^etc. )

The present invention will now be described by way of example with reference to the accompanying drawings, which illustrate an embodiment of the sensor of the present invention shows in longitudinal section.

The container 1 shown in the drawing is made of a ceramic material that contains the solid electrolyte forms, whereby its inner wall 2 and / or its outer wall 3 comes into contact with an oxide (an oxygen-sensitive Electrode).

The internal reference compartment uses a chemical system consisting of either a gaseous mixture (e.g. pure C ^, Air, an oxygen gas mixture, CO / CO ^ or FU / HpO mixtures) or a metal oxide mixture, e.g .: Ni, NiO, Fe-FeO etc., to establish a known partial pressure of oxygen.

The internal reference compartment is used as an oxygen sensitive one Electrode either a noble metal or an oxide.

The outer electrode lies in the gas atmosphere to be analyzed, and their oxygen sensitive material is either an oxide or a mixture of oxides.

Under operating conditions, an electromotive force (EMF) is observed between electrodes 2 and 3, such as this is indicated schematically. It is the value of this EMF that gives the measure of oxygen activity.

The apparatus according to the present invention can be used industrially in the following fields:

a) Monitoring the atmosphere during the heat treatment of Metals;

b) Combustion monitoring in steam generators, furnaces and steam boilers;

c) monitoring of exhaust gases from internal combustion engines and

d) improving fuel economy and Antipollution device.

Ma / MP - 9 -

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Claims (19)

Claims 1.; Solid oxygen sensor for measuring oxygen partial press, characterized in that it is formed by an electrolytic cell whose non-stoichiometric electrodes sensitive to oxygen Oxides are while the electrolyte is a solid ceramic. 2. Solid oxygen sensor according to claim 1, d a d u r c h characterized in that the oxygen-sensitive Electrodes mixed conductivity, ionic and oxides electronic, are. 3. Solid oxygen sensor according to claim 1, d a d u r c h characterized in that the oxygen-sensitive Electrodes are oxides that are the potential poisoning metal contained in the gas atmosphere to be analyzed. 4. Solid oxygen sensor according to claim 1, d a d u r c h characterized in that the oxygen-sensitive Electrodes are mixed oxides that contain two or more cations. BERLIN: TELEPHONE (030) 8312Ο88 CABLE: PROPINDUS TELEX: 184057 MUNICH: TELEPHONE (Ο89) 225585 CABLE: PROPINDUS TELEX: 524244 5. solid oxygen sensor according to claim 1, characterized in that the oxygen-sensitive electrodes are oxide mixtures are. 6. Solid oxygen sensor according to claim!, Characterized characterized in that the cell is formed by a solid ceramic container of one wall is in contact with the oxides that make up the oxygen sensitive electrode. 7. solid oxygen sensor according to claim 1, d a d u r c characterized in that the cell is formed from a solid ceramic container, both of which Walls are in contact with the oxides that make up the oxygen sensitive electrodes. 8. solid oxygen sensor according to claims 1 to 5, characterized in that one wall of the cell is in contact with mixtures of the oxides which is the oxygen-sensitive electrode form. 9. Solid oxygen sensor according to one of the claims to 5, characterized in that both walls of the cell are in contact with mixtures of the oxides. 10. Solid oxygen sensor according to one of claims 1 to 4, characterized in that the outer wall surface of the cell is ^{bescniclrtet with p} r ° 2-x. 11. Solid oxygen sensor according to one of claims 1 to 4, characterized in that the outer wall surface of the cell is coated _{with TbO 9.} 12. Solid oxygen sensor according to one of claims 1 or 6, characterized in that the outer surface is coated with TbO ₉ + and / or PrO ₉ + CeQ ₉ . 13. Solid oxygen sensor according to one of claims 1, 2 or 4, characterized in that the outer surface is coated with oxides of lanthanides is. 14. Solid oxygen sensor according to one of claims 1, 2 or 6, characterized in that that the outer surface is coated with mixed oxides of lanthanides and / or transition metals. 15. Solid oxygen sensor according to one of claims 1 or 6, characterized in that that the outer surface of the solid electrolyte with mixed oxides of at least one of lanthanides, Transition and alkali metals is coated. 16. Solid oxygen sensor according to one of claims 1, 2 or 6, characterized in that that the outer surface is mixed with oxides of at least one of lanthanides, transitional and Al kaiierdmetallen is coated. 17. Solid oxygen sensor according to one of claims 1, 2 orö, indicated by that the outer surface of the solid electrolyte with mixed oxides of at least one of lanthanides, Transition and alkaline earth metals is coated. 18. Solid oxygen sensor according to one of claims 1, 2 or 6, characterized in that the cell is formed by a solid ceramic container one wall of which is in contact with a precious metal and the other wall is in contact with the oxides mentioned in the preceding claims. 19. Solid oxygen sensor according to one of claims 1, 2 or 6, one or both of which walls are in contact with mixtures, single or complex, one in the preceding Claims of claimed material are located. - 27 844 - 5 -